nfs: set vs_hidden on nfs4_callback_version4 (try #2)

This service should not be registered with or unregistered from rpcbind.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/callback_xdr.c

@@ -987,4 +987,5 @@ struct svc_version nfs4_callback_version4 = {
 	.vs_proc = nfs4_callback_procedures1,
 	.vs_xdrsize = NFS4_CALLBACK_XDRSIZE,
 	.vs_dispatch = NULL,
+	.vs_hidden = 1,
 };